BEIJING—President Xi Jinping's anticorruption drive reached into the heart of the military elite as the Communist Party expelled its highest-ranking official yet in the effort, accusing one of China's most senior retired generals of taking bribes.

Gen. Xu Caihou, a former vice chairman of the Central Military Commission, which controls China's armed forces, is the top military figure to be publicly accused of corruption in at least 35 years. As a former member of the party's 25-member Politburo, he is also the highest...